Sciencemadness Discussion Board

Compounds produced when electrolysis of water is performed

polymer - 16-8-2007 at 12:34

When I perform electrolysis of water (with citric acid), two chemicals are observed (a blue chemical and a black chemical). What are those?

Xenoid - 16-8-2007 at 12:51

Depends a bit on what materials you used for your anode and cathode!.....:o

I guess at least one was copper......

Xenoid

[Edited on 16-8-2007 by Xenoid]

polymer - 16-8-2007 at 13:11

My anode and cathode are both copper. I agree with you on the copper part. What are the best metals to use as anodes and cathodes?

ssdd - 16-8-2007 at 13:23

Yea I just tried this with a copper cathode and anode. I got the blue and black substance as specified, not sure what they could be off hand but I could guess and say perhaps copper citrate or something of the like?

Would be interested to know as to what they really are...

-ssdd

** The blue substance is being formed around the negative electrode.

[Edited on 16-8-2007 by ssdd]

Xenoid - 16-8-2007 at 14:30

The black material will be CuO (Cupric oxide, black copper oxide).

If you are trying to make oxygen and hydrogen the best materials for a simple cell like this would be the graphite (carbon) electrodes removed from old lantern batteries (not the newer alkaline type, but the old zinc carbon). You can find plenty in old lanterns at recycling centres, etc.

Xenoid

not_important - 16-8-2007 at 15:07

Alternatively, if H2 and O2 are what you are after, nickel or stainless steel electrodes in sodium or potassium hydroxide electrolyte works well, carbonate can substitute for hydroxide but is less effective.

Using carboxylic acids in electrolysis can lead to Kolbe electrolysis reactions.
http://www.organic-chemistry.org/namedreactions/kolbe-electr...

With an organic acid like citric acid you could get quite a complex mixture of products. On top of that the citric acid will for complexes with copper, speeding the dissolving of the electrode.

16MillionEyes - 20-8-2007 at 19:08

Quote:

If you are trying to make oxygen and hydrogen the best materials for a simple cell like this would be the graphite (carbon) electrodes


You could also get it easily from pencils leads but don't use very thin ones as it appears the current 'flakes' off some of the external layers leaving you an undesirable black residue.